1. Field of the Invention
The present invention relates generally to video systems, and more specifically, to a method and system that adaptively alter a buffered video rate in response to an indication of video quality.
2. Background of the Invention
Digital audio and video systems are prevalent in the areas of home entertainment, professional production of multimedia and computer reproduction and generation of multimedia sources. In particular, systems that record a video stream are frequently coupled to source devices such as cameras and also produced from AV playback devices such as video cassette recorders (VCRs), digital versatile disc (DVD) players and compact disc (CD) players.
The above-incorporated U.S. patent applications disclose methods and system for sampling and re-clocking video data derived from an input video source for the purposes of recording or processing the video data. However, there is a significant difference between a system optimized for processing a very stable video source signal, such as that produced by a camera or DVD player and a system optimized for processing a relatively unstable source, such as that provided by a VCR.
Due to the mechanical extraction of video information that occurs in a VCR, mechanical variations (jitter) in the video signal (pixels) cause the length and position of lines to vary dramatically. The field synchronization is typically more stable, as the vertical fields are synchronized with the vertical sync signal generated by the head pulses. The variations in line position are typically uncompensated, particularly in consumer VCRs, so the line-to-line variation typically requires buffering an entire field of video in order to produce a stable output representation for sampling. Also, because of the need to provide stable synchronization information in the output video that is locked to the source rate of the video, a slow response (i.e., low bandwidth) clock generator is typically required to generate the output video synchronization signal.
However, for stable video sources, it is desirable to have a shorter buffer and a more responsive clock generating circuit, so that acquisition time and latency are reduced, as well as cost associated with the video buffer, which can be a large amount of memory at the high sampling and oversampling rates required for video capture.
Therefore, it would be desirable to provide a method and system for stabilizing a sampled video signal from an unstable input video source with minimum buffer space. It would further be desirable to provide such a method and system that has a fast acquisition time and low latency for high-quality video signal sources, while maintaining a sufficiently stabilized clock generator and buffering for lower-quality video signal sources. It would also be desirable to provide such a method and system that automatically adapt to the quality of an input video signal.